Treatment With Spinal Cord Stimulation: Effect on Sensory Parameters

The primary purpose is to study the effect of spinal cord stimulation (SCS) on sensory parameters, using quantitative sensory testing (QST). Patients with established SCS treatment will be examined with QST. Subjects will be randomized to have their SCS device turned off or kept active (1:1) for a 12-hour period, then be reexamined using the same QST protocol. After the 2nd examination all patients cross over (ie. inactive devices are activated, active devices are deactivated) and are reexamined after a new 12-hour period. The investigators expect to demonstrate that SCS treatment has a significant effect on sensory parameters associated with pain hypersensitivity but no significant effect on sensory parameters associated with detection of non-painful stimuli.